In general, a fuel combustion control system for use in a boiler, particularly a middle-sized or small-sized boiler with the steam pressure controlled to a desired value comprises a fuel valve for controlling the fuel flow rate and an air damper for controlling air flow rate which are connected with each other by a connecting means such as a link member or a cam means. In such a fuel combustion control system, in order to achieve complete combustion of the fuel, it is required to maintain the fuel flow rate and the excess-air ratio in a required relation. For this purpose, according to the conventional method, it is necessary to obtain data indicating the relation between the opening degree of the fuel valve and the fuel flow rate and the relation between the opening degree of the air damper and the air flow rate by preliminarily operating the fuel combustion control system with the boiler in advance to actual operation of the same, whereby the link member between the fuel valve and the air damper is controlled by the operator on the basis of said data so that desired complete combustion can be achieved.
However, in the conventional fuel combustion control system, since the relation between the opening degree of the air damper or the fuel valve and the volume of air in the burner of the boiler is liable to be delicately changed, the link member should be controlled repeatedly, requiring skill and intuition of the operator.
For overcoming the aforementioned disadvantage, the inventors proposed a fuel combustion control system by relating Japanese patent application No. 81374/1981 which aims at simple and reliable operation of the fuel combustion control system by preliminarily operating the control object, such as a fuel combustion control system, for use in a boiler to obtain data indicating the relation between the opening degree of the fuel valve and the fuel flow rate, the relation between the opening degree of the air damper and the air flow rate and the relation between the fuel flow rate and the excess-air ratio, based on which the opening degrees of the fuel valve and the air damper are automatically and appropriately controlled.
However, the fuel used in the fuel combustion control system, e.g., G heavy oil is not always manufactured under the same conditions, and the physical characteristics, especially kinematic viscosity of the fuel, are fluctuated by heating of the fuel for facilitating atomization thereof in the burner and by fluctuation of the pressure at the pump for supplying the fuel, leading to errors between the estimatcd data of the relation between the fuel flow rate and the valve opening degree and the relation between the fuel flow rate and the excess-air ratio and the actual values thereof in actual operation of the fuel combustion control system, thereby causing reduction of accuracy in the controlling operation.
For overcoming the aforementioned disadvantage, it may be considered to update the aforementioned data whenever the manufacturing condition of the fuel is changed and the heating temperature of the fuel for atomization thereof is changed, though, in this case, the updated data must be manually re-inputted into the system, leading to reduction in operation workability.